| Summary: | 碩士 === 輔仁大學 === 食品營養學系 === 88 === Modulation of Antioxidants and Folate Related Nutrients on Homocysteine Thiolactone Induced Apoptosis in Mammalian Cell Lines
Shu-Mei Huang
Abstract
The cytotoxicity of homocysteine on localized tissues other than from circulatory system is not well established. The present study revealed that human promyeloid leukemia HL-60 cells were induced apoptosis by homocysteine derivatives (HcyT) treatment at pathological concentrations. Apoptosis induced by HcyT was characterized by increased phosphatidylserine (PS) exposure on the cell membrane surface, increased apoptotic cells with hypoploid DNA contents, and internucleosomal DNA fragmentation, all of which occurred in a time- and dose-dependent manner. HcyT treatment also significantly increased intracellular reactive oxygen species H2O2 and caspase-3 activity, which was accompanied by the appearance of apoptotic features. Addition of caspase-9 inhibitor to HcyT-treated HL-60 cells delayed caspase-3 activation, but could not completely prevent cells from apoptotic damage. Preincubation of HcyT-treated HL-60 cells with catalase completely scavenged intracellular H2O2, thus inhibiting caspase-3 activity and protecting cells from apoptotic DNA damage and membrane injury. Conversely, antioxidants of NAC, Vit C and Vit E partially inhibited HcyT-induced H2O2 production、caspase-3 activation and apoptosis. Neither SOD nor Hcy- metabolizing nutrients (folate, vitamin B6 and B12) had the significant effects on the prevention of HcyT-treated HL-60 cells from apoptotic damage. Chinese hamster ovary cells (CHO) were less sensitive to HcyT-induced cytotoxicity than HL-60 cells. Cells with mitochondrial defects were more sensitive to HcyT-induced cell growth arrest than cells with cytosol defects. Taken together, these results suggest that different cell types have different susceptibility to HcyT toxicity. HcyT treatment induced apoptosis in HL-60 cells through H2O2 generation, and caspase-3 activation. Antioxidants of NAC、Vit C and Vit E could partially reduce HcyT-exerted apoptotic damage. Addition of folate、Vit B6 and B12 had no significant effects on HcyT-induced apoptotic damage, yet intercompartment folate metabolism could modulate HcyT-induced cytotoxicity.
Key words: homocysteine thiolactone、apoptosis、H2O2、caspase-3、CHO、HL-60
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